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## Re: [Amps] *** SPAM *** Re: Antenna traps

 To: Steve Thompson Re: [Amps] *** SPAM *** Re: Antenna traps Ian White GM3SEK Ian White Fri, 16 Dec 2005 16:06:48 +0000
 ```Steve Thompson wrote: > > >Ian White GM3SEK wrote: > >> >> Let's think of two totally generalized impedances, (R1 in series with >> jX1) and (R2 in series with X2). In this context X1 and X2 can have >> either sign. >> >> Now add series elements -X1 and -X2 to cancel both reactances out. We >> now have resistive impedances R1 and R2, which can be matched with the >> minimum-Q solution using two elements in one of the L-network >> configurations. >This is where I started - but you can always add a first element to take >you to a pure resistance that's nearer your target than (say) R1 is. >Then, the L match from the new resistance to target will have a lower Q >than the one from R1 to target and the three elements give you lower Q >than two. > >I think the train of thought can be valid where you can't choose >whichever of the L match permutations is needed for minimum Q - that's >the trap I fell in to. That's a fair point. The more elements you add, the more possibilities you have to synthesize a network that transforms the impedance in a cascade of small steps. Then, as Peter points out, it begins to look a lot like a filter... and disappears into a cloud of complex maths. In practical terms, a very nice thing to do with a large T-tuner is the mod suggested by G3LNP: fit a cam switch to each capacitor, so that rotating it to maximum capacitance will short the cap completely. This gives the user an instant choice between a T-network, a step-up L-network or a step-down L-network. Tune for minimum smoke. -- 73 from Ian GM3SEK _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps ```
 Current Thread Re: [Amps] *** SPAM *** Re: Antenna traps, Peter Chadwick Re: [Amps] *** SPAM *** Re: Antenna traps, R . Measures Re: [Amps] *** SPAM *** Re: Antenna traps, Steve Thompson Re: [Amps] *** SPAM *** Re: Antenna traps, Ian White GM3SEK Re: [Amps] *** SPAM *** Re: Antenna traps, Steve Thompson Re: [Amps] *** SPAM *** Re: Antenna traps, Ian White GM3SEK Re: [Amps] *** SPAM *** Re: Antenna traps, Steve Thompson Re: [Amps] *** SPAM *** Re: Antenna traps, Ian White GM3SEK <=